Poster C99, Sunday, March 25, 1:00-3:00 pm, Exhibit Hall C
Fast fMRI with simultaneous EEG detects distinct thalamocortical dynamics underlying transitions in and out of sleep
Laura Lewis1,2, Jonathan Polimeni2,3, Kawin Setsompop2,3, Robert Stickgold4, Giorgio Bonmassar2,3, Bruce Rosen2,3; 1Harvard University, 2Massachusetts General Hospital, 3Harvard Medical School, 4Beth Israel Deaconess Medical Center
Sleep onset is a gradual process marked by changes in electrophysiological dynamics and a progressive decline in perception, consciousness, and behavior. Thalamus is a key regulator of cognition and neurophysiology in sleep, but thalamic activity cannot be measured through scalp EEG, so little is known about how dynamics in human thalamus contribute to the process of sleep onset. We aimed to track shifts in thalamocortical dynamics at high temporal resolution within the human brain during sleep onset. We developed a new approach to imaging local thalamocortical dynamics in the 0.1-1 Hz range by performing simultaneous EEG and fast (TR<400 ms) fMRI, allowing rapid imaging of local thalamic and cortical oscillations. We scanned 14 subjects with EEG-fMRI at 3 Tesla and 5 subjects at 7 Tesla during sleep. We found that declining arousal during sleep onset was marked by the appearance of slow (0.1-1 Hz) coherent thalamic and cortical fMRI dynamics. The phase of the fMRI oscillation was coupled to the spectral content of the EEG, suggesting a correspondence with oscillations in local neural excitability. In contrast, awakening was signaled by an early-onset thalamic activation and delayed cortical activation, suggesting a distinct, thalamus-mediated mechanism for arousals from sleep. We conclude that transitory shifts in the coherence of local slow thalamocortical dynamics predict moment-to-moment arousal state. These results demonstrate that rapid changes in large-scale network function can be detected through new techniques for fast whole-brain neuroimaging, and identify distinct thalamic and cortical activity patterns that signal transitions into and out of sleep.
Topic Area: PERCEPTION & ACTION: Other